The present invention relates to an arrangement for the inductive querying of and supplying of power to an isolated circuit having an electrical consuming device.
In European Patent Application 183 580, an inductively operating arrangement is disclosed for the transmission of driver-based commands, particularly from the steering wheel of a motor vehicle, to the steering column or to the vehicle chassis. It is suggested there that the secondary winding of a rotary transformer, which, rotatably with respect to the steering column, is connected with the steering wheel, can be loaded, for example, by resistance added to the circuit in a defined manner so that a secondary loading of the rotary transformer is obtained which can be coded according to the driver's intention and sensed at the primary side of the transformer on the steering column. For this purpose, an approximately constant alternating current is provided on the primary side, so that a resulting alternating voltage at the primary winding can be measured to provide a measurement of the load made available on the secondary side. In this sense, the alternating voltage will then be peak-value-rectified and quantized in order to assign different driver commands to different load conditions.
That arrangement, however, does not carry out any testing or monitoring query of the circuit to ascertain whether the resistances 53 to 57 to be controllably added to the circuit actually correspond to defined desired values (within permissible tolerances), and were not changed unacceptably by aging or defects. As a result, a faulty resistance in any arrangement may easily be analyzed to be an incorrect driver-based command.
For corresponding reasons, in any arrangement, the isolating transformer must be manufactured with high precision and, for example, in the case of a rotary transformer, must be manufactured with close tolerances of the air gap and of the leakage inductance with respect to the angles of rotation and over the operational lifetime of the transformer. Otherwise, certain tolerances or changes of the transformer, on the primary side, may simulate incorrect load conditions, on the secondary side, and lead to incorrect interpretations of driver-based commands.
It is also unsatisfactory that no possibility exists in the above-noted arrangement to query the condition of the transformer. Because of the high cost of a precisely manufactured and mountable rotary transformer as well as because of the indicated inherent safety defects, the known device is not suitable, for example, for use in an occupant protection system of a vehicle which must be available for operation at any moment.
In European Patent Text 87 138, a device is also disclosed for the inductive supplying of power to a circuit arrangement which is rotatably provided at vehicles. That text discloses the supplying of a pressure sensor as a component of a tire pressure monitoring device. That arrangement provides the supplying of operating power to a data acquisition and transmitting device by a rotary transformer. For this purpose, the primary side and the secondary side of the rotary transformer are constructed to be rotatably movable with respect to one another. The inductively transmitted power is used mainly for controlling an optoelectronic emitter (LED) having an output corresponding to an actual pressure value in order to transmit the pressure value by way of light from the rotatable circuit part to the stationary port. For this purpose, an optoelectronic data receiver is provided in the stationary circuit part and controls a device for displaying or representing the momentary measured value and a discriminator circuit which reduces the control power of the transformer.
Because of high losses when the power demand of the noted circuit arrangement is high on the secondary side (data transmission; operation), this discriminator circuit is provided in order to achieve a reduction of the power loss, particularly in the rotary transformer, when the power demand on the secondary side is low (no data transmission; standby), by a reduction of the control power of the rotary transformer to a standby value, and, as a result, considerably increase the efficiency of the device during standby periods. On the whole, the aforementioned arrangement aims at an overall operating power that is as low as possible, and therefore at a control power of such a transformer that is as low as possible when the power demand on its secondary side is also low.
The query or transmission of status information in the case of safety devices, for example, at a manufacturing machine or in a motor vehicle, and particularly of a type of information that is needed only in emergency situations (such as reports of danger, accident), requires a maximum availability of the information. Thus, simplicity is required and as a result it is desirable to use the smallest possible number of structural elements which have a proven, high, long-time reliability. Even for modern LEDs, the reliability characteristic of the device applies only to a limited extent if they are subjected to extreme stress, as, for example, in a motor vehicle. The danger of the effect of dirt also impaired the availability of a testing device where a testing signal is obtained optically from the moving part. Thus, a use of the aforesaid arrangement for the contactless query of a safety-relevant output variable could hardly promise a sufficiently reliable availability of operation because of the problems associated with LED operation as well as an excessive number of required structural elements.
It is, therefore, an object of the present invention to provide, in a particularly simple manner, an arrangement for the inductive querying of the operational status of an electrical consuming device, such as a triggering device of an air bag occupant restraining system, such that a testing of the consuming device and of its electrical circuit with respect to its faultlessness is possible in a simple way.
It is another object of the present invention to provide an arrangement wherein certain deviations of the transmission characteristics of an inductive transmitting device, for example, an isolating transformer, resulting from the manufacturing process, can be compensated and are therefore permissible.
It is a further object of the present invention to provide an arrangement wherein it is possible to test this inductive transmitting device itself in the course of a testing or monitoring of the consuming device.
Without any loss of definiteness of the test information concerning the operational status of the consuming device to be queried, it is an advantageous feature of preferred embodiments of the present invention that a cost-effective isolating transformer, with less stringent manufacturing and mounting tolerances, is used as a result of the fact that the isolating transformer is provided twice. Any tolerances of the two transformers, with respect to one another, are compensated by the fact that they each equally supply the consuming device in a first current path and a consuming device simulation in a second current path with a testing current, and that the querying of both loads represented by the consuming device and simulation device takes place by special read out winding which are associated with both transformers. As a result of the two-path feeding of testing current and querying, the arrangement permits the recognition of a defect at a transformer.
It is an additional object of the present invention to provide an arrangement of the type noted above which, under certain conditions, supplies a definite operating power to the consuming device in a particularly effective manner.
Certain preferred features of embodiments of the present invention provide the advantage that, when the feed current is low, it permits the comparing of the consuming device with a simulation device of the consuming device by a test current which is equalled proved by to both the consuming device and simulation device. However, when a higher operating current is provided, a predominant part of the feed power is fed to the consuming device as operating power and only a small part of the feed power is provided to the simulation device as a power loss, so that the consuming device-related power transmission efficiency increases considerably when the feed current of the arrangement is increased and as a result permits a low-cost design of a feed generator circuit which generates the total feed power. Thus, additional measures for avoiding unnecessary power losses in the querying operation are not required.
Other objects of the invention include further developing the arrangement according to the teachings of the present invention wherein, by means of feeding and analyzing devices provided, it is always possible to continuously and extremely reliably test the consuming device and its availability and reliably start operation of the consuming device from the testing status state and that the occurrence of a defect of the consuming device cannot remain unnoticed under any circumstances.
In addition, a further feature of the invention is the ability to issue at least one command from the isolated circuit without, in any way, limiting the ability of the consuming device to be tested.
All in all, the arrangement according to the preferred embodiments of the present invention offers the advantage of a simple circuit for testing, as well as for operating, an isolated consuming device. In addition to inductive isolating transformers, the arrangement comprises, in its basic structure, only three additional, identical structural elements, and a device simulating the consuming device. The transmission of the operating and testing power as well as the querying of the operational readiness of the consuming device take place by the same air gap of a doubled isolating transformer. With the simultaneous comparison of the consuming device with a simulation via alternating feeding and querying paths, a testing voltage and a reference voltage are formed which, also without any booster amplification or other additional supplementary circuitry (i.e. reasonably with respect to cost), is capable of directly controlling modern microcomputers and their standard interfaces with a high signal-to-background noise ratio.
Without any impairment of the querying operation of the consuming device and its simulation, a low direct current may also be derived from the isolated circuit. For example, the low current can be provided as a power supply for the operation of a small computer and/or display device, which may also be backed up, in a nonvolatile manner, by a bufferable power source, such as a secondary battery or a high-capacity capacitor.
The use of only a few proven structural elements, having a high reliability of operation, results in a high reliability of operation of the arrangement and permits its application as a component of safety systems. In this connection, it is suitable, for example, for the testing and, if necessary, also for supplying power to a triggering device or triggering dot at the steering wheel of a motor vehicle which is essential for safety purposes such as, for example, in an occupant restraining air bag system.
The arrangement, which is further developed by supplementary feeding and analyzing devices, also permits a cableless triggering or actuating of at least one operating device remote from the isolated circuit. For example, the horn or the emergency flasher system of a motor vehicle may be triggered. The various embodiments of the invention, which are provided for this purpose in many different designs, open up additional efficient safety functions for recognizing a defect and for ensuring its fast elimination.
One embodiment of the present invention utilizes the amplifierless direct-controllability of a modern single-chip A/D micro-controller in which a plurality of analog functional elements are not required. Acquisition of command data and status quantities as well as associated processing into operating signals or defect reports is accomplished exclusively by software. Among other things, this arrangement, when it is programmed appropriately, can learn its own manufacturing tolerances, permitting a soft compensation of its specific tolerances. In a vehicle, it may, for example, cooperate with a vehicle management computer for the processing of service demands by voice output.
Although the arrangement, in accordance with preferred embodiments of the present invention, is discussed for use in a motor vehicle and its method of operation is explained by an illustrative application of embodiments to a motor vehicle, the possibilities for its use are by no means limited to a motor vehicle. The arrangement may equally well be used in water vehicles, track-guided vehicles, air and space vehicles, underground in a potentially explosive environment or even at operating interfaces of machine tools.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.